Military strike aircraft are designed to carry and release a wide range of weapons and other "stores" (bombs, for example) while in flight. Aircraft used to deliver stores in flight typically incorporate release and ejection equipment (ejector racks) located beneath the wings and fuselage that are designed to release the stores upon command during flight. Typical ejector racks are disclosed in U.S. Pat. Nos. 4,043,525 and 4,347,777, both of which are assigned to an affiliate of the entity to which the present invention is assigned.
A typical stores ejection system mechanically releases and forcibly ejects the store away from the aircraft slipstream upon command. Conventionally, pneumatic ejector piston rams housed within the ejection rack are forced outward against the store in response to the sudden release of pressurized fluid. Store release hooks that engage store structural attachment members known as "bail lugs" are opened simultaneously, and the store is forcibly ejected away from the aircraft body.
A modern ejector rack system is disclosed in U.S. Pat. No. 5,583,312 to Jakubowski, in which a pneumatic ejector rack having a single on-board pressurization system for initiating multiple release mechanisms is disclosed. The Jakubowski system uses filtered pressurized air as an energy storage fluid. Since the compressor system is on-board, a constant pressure may be maintained independent of outside temperature and pressure changes. In operation, the pressurized gas from the accumulator, when released through a feed port, opens store release hooks and simultaneously forces ejector pistons outward, thereby forcibly releasing and jettisoning the store.
Conventional stores ejection systems are designed to accommodate conventional stores. The United States military has published military standard MIL-STD-2088A, which provides specifications for ejector rack systems to eject conventional stores with diameters between 8.0 and 30.0 inches at up to 22,500 pounds of ejection force. MIL-STD-2088A is incorporated herein by reference. Based on store weight and diameter, MIL-STD 2088A specifies the interface between the ejector rack and two classes of store. For stores weighing up to 1,450 pounds and with diameters between 8.0 and 20.0 inches, the ejector rack must engage the store with two appropriately-sized bail lugs spaced 14.0 inches apart along the length of the store. For stores weighing up to 5,000 pounds and with diameters between 8.0 and 30.0 inches, the ejector rack must engage the store with two larger bail lugs spaced 30.0 inches apart along the length of the store. Conventional stores ejection systems thus comprise two store release hooks spaced apart by either 14.0 inches or 30.0 inches and sized to engage bail lugs for stores in either of two weight classes.
Defense industries around the world are developing new "miniature munitions" that are considerably smaller and lighter than conventional stores, with diameters less than 8.0 inches and weights under 500 pounds. Conventional stores ejection systems are not well-suited to accommodate these new miniature stores for several reasons. First, ejector racks designed to comply with MIL-STD-2088A include two store release hooks separated by either 14.0 inches or 30.0 inches. The conventional configuration of two widely-spaced hooks is too large to accommodate miniature stores, some of which are less than 30 inches in length. Moreover, conventional ejector racks include integral swaybraces sized to provide swaybracing to conventional stores, which have diameters greater than 8.0 inches. The swaybraces on conventional ejector racks cannot provide adequate swaybracing to miniature stores.
Two-hook ejector racks allow independent loading of each of the two store bail lugs into each of the two hooks. The two hooks must be opened simultaneously, however, to properly release the store. The requirement that the hooks be loaded independently but opened dependently dictates the use of a complex mechanical linkage between the hooks in a conventional two-hook stores ejection system.
Moreover, bail lugs designed to be engaged by conventional ejector racks are large relative to the size of the miniature store (protruding approximately 1.55 inches above a store that is less than 8.0 inches in diameter). A relatively large bail lug degrades store aerodynamic performance, and hence store delivery accuracy, and results in higher radar cross section for the store. Miniature stores can use alternative hook engagement devices that are smaller and more aerodynamic than standard bail lugs, however conventional ejector racks are not compatible with these alternative devices.
Conventional two-hook stores ejection systems, therefore, suffer from the limitations discussed above. In particular, conventional stores ejection systems cannot provide adequate swaybracing to miniature stores with diameters less than 8.0 inches. Conventional stores ejection systems are also not suitable for use with smaller stores because the relative size of the store bail lugs required to mate with conventional ejector racks results in increased store aerodynamic drag and radar signature and reduced store delivery accuracy. In addition, conventional stores ejection mechanisms with two release hooks include a complex hook release mechanical linkage.